The present invention relates generally to pressure sensitive label sheets, useful for duplexing applications. The invention is particularly applicable for example, to Integrated, Fuse Form(trademark), Dual Web or Full Sheet laser label sheets for duplex printing applications.
Pressure sensitive labels are commonly available in various forms. In a typical embodiment, a label sheet includes several individually removable labels which define an overlay or face sheet adhesively bonded to a release liner. The adhesive is permanently bonded to the back of the overlay, and forms a weak bond with the liner which typically has an exposed silicone surface permitting individual label removal therefrom.
The individual labels are typically defined by full perimeter die cuts which completely sever adjoining labels from their neighbors atop the continuous liner. By lifting the edge of an individual label, the label may be readily peeled away from the liner independently of adjacent labels, with the so removed label then being reattached to another surface using the same adhesive carried on the back of the label for effecting a bond therewith, which is typically permanent.
The adhesive must be suitably tailored in strength for maintaining integrity of the entire label sheet to prevent premature delamination of any of the individual labels thereon, while also permitting individual removal of the labels, with the perimeter die cuts preventing simultaneous multiple label removal.
It has been known to provide ties between adjoining labels, if it is desired to simultaneously remove two or more labels together. Several such ties may be spaced apart around the perimeter of adjoining labels so that removal of one label carries with it the so tied adjoining label in a serial strip of labels. The so removed individual labels may then be separated from each other by severing or tearing the joining ties.
It was also know to provide ties between labels used in simplex (single pass printing) applications in order to prevent delamination of labels. The problem primarily addressed there was extreme delamination, particularly of smaller labels provided with narrow feed strip caused by friction with the printer rollers (see U.S. Ser. No. 09/259,116, filed Feb. 26, 1999). The ties were thus only necessary on the smaller labels and only on the side first passing the printer roller.
In use, labels are printed for various reasons. For example, a pharmacy script is a specialized label sheet having differently sized and configured individual labels for different objectives. Relatively large labels may be used for identifying dispensed drugs and corresponding use instructions. Smaller labels may contain various warnings. And, an associated paper form integrated with the label sheet may include various information regarding the nature of the drug being dispensed and various instructions and warnings.
Pharmacy scripts are available in different configurations for various reasons. The primary objective of the pharmacy script is the labeling of prescription drug containers in a highly competitive industry. Since a typical pharmacy or drugstore dispenses a considerable volume of drug prescriptions each day, the pharmacy script must be easy and fast to use.
In one recently developed pharmacy script, several wide and narrow labels are formed laterally along a thin strip at the leading edge of the label sheet. The leading edge strip defines the feeding direction for the sheet and its orientation so that various information may be printed atop the various labels of the label sheet in the same configuration as multiple sheets are fed through a printer, such as a typical laser printer. In an initial prototype, the various labels contained full perimeter die cuts to ensure the individual removal thereof when desired. The individual labels must be readily removable without delay or damage to maximize the efficiency of label application to their containers.
It has been known to provide labels for duplex printing, i.e., printing on two sides by passing the media through the rollers, toner and fuser assembly twice. However, the additional heating by two runs through the fuser and the extra manipulation of the media needed to turn it around and run it through the printer process again exacerbated the delamination problem and the problem of adhesive coming off the media into the printer.
The inventors have discovered that, when pressure sensitive adhesive labels are used for duplexing applications, they are subject to move roller passes, e.g. de-curl bars, and to more heat than in simplex applications. For instance, prior to passing the de-curl station, the substrate passes through the fuser assembly which melts the toner for anchorage to the substrate. The heat indiscriminately softens the adhesive. This softening together with the stress applied as the substrate is manipulated at an acute angle throughout the printer, duplex unit, and de-curl station causes separation of labels at the die cuts and leakage of the adhesive to the surface. This separation exposes the adhesive to various parts in the printer path. This causes adhesive build-up in the printer and eventual undesired jamming, misfeeds and skewing. Such problems often put the machine out of service requiring attention by a trained service person. It can also damage the fuser assembly and duplex unit.
To avoid these disadvantages, the inventors have discovered that duplexing is improved by tying the die-cut pressure sensitive labels together, and/or to; edges, a matrix, waste strips etc., of the media. Tying the individual labels retains them in juxtaposition and keeps them from separating. The material therefore travels through the de-curl unit with labels intact and little or no leakage of adhesive into the printer. The ties can be strategically placed to fall directly in line with drive rollers within the printer. In order to improve the feed performance of die cut materials within a duplexing operation, during the die cutting process, a xe2x80x9ctiexe2x80x9d is added in one or more places to link the several die-cut shapes together. Creating a void or dull place within the cutting surface of the die is a preferred way to create a tie. The die cuts as it is designed, except in the void area, thus leaving an uncut section. The uncut section is the tie which continues to attach the individual die-cut sections. Ties prevent the die-cut sections from pulling apart and exposing adhesive within the printer.
According to the invention, the pressure sensitive label sheets, whether of the pharmacy script configuration described above, some other pharmacy script configuration or some other label application, are subject to duplex printing. As described above, the labels are accordingly provided with ties between the labels and other labels, the edges of the sheet, a matrix area, a waste area, etc., of the sheet. The ties are preferably provided by leaving a small area defining the tie not die cut. One or more ties can be provided for a particular label. In one embodiment, multiple ties are provided symmetrically spaced around the label. In another embodiment, one or more ties are provided only at the leading and trailing edges of the label, in terms of the direction of the sheet passing through the printer. In another embodiment, ties are strategically placed to coincide with where the drive rollers of the printer contact the sheet in order to provide additional stability where this friction occurs.
As described above, the invention is particularly useful when the adhesive used in connection with the labels is prone to softening when subject to the heat from the fuser in the printer, for example, at about 400-500xc2x0 F. The ties keep the label in place, particularly as the sheet is subject to an acute angle to facilitate duplexing, so as to prevent the softened adhesive from leaking off the sheet onto the printer parts. However, the invention can also be applied in applications where the adhesive would not soften in the printer operation, e.g., in cold fuser assemblies or where non-melting adhesives are used. This is because the ties are useful also for preventing delamination which may occur due to the acute angle the sheet is subject to during duplexing.
The laser printers useful in connection with the tied labels of the invention include those known in the art and commercially available, including duplex printers manufactured by LexMark International, Lexington, Ky. The construction and operation of duplex printers are known in the art and need not be described here further.